This invention relates to a rectifier assembly for use on the rotor of a synchronous machine such as a brushless alternating current generator or a brushless synchronous motor.
A synchronous machine, such as a brushless alternating current generator, has an exciter generator comprising a DC stator field with an AC armature on the rotor. A rectifier on the rotor rectifies AC from the exciter for the main generator DC field winding which is also located on the rotor. The main AC armature is on the stator and the AC voltage is available therefrom. An example of such a machine is provided by Sones et al U.S. Pat. No. 3,059,168. The rectifier typically uses individual semiconductor diode rectifiers mounted in a housing on the rotor shaft. Several disadvantages are encountered when employing individual semiconductor diode rectifiers. For example, mounting complexity is encountered due to the physical stresses from the rotational "G" forces at speeds up to 20,000 RPM, which are used in aircraft generators and motors. Also, since the casing of the semiconductor diode rectifier is usually the anode or the cathode of the device, the rectifier must be insulated from the mounting base if the mounting base is conductive. Moreover, reliability of the rectifier is degraded due to the complexity of the entire rectifier assembly. Also, effective cooling of the semiconductor diode rectifier is difficult as there is a high thermal resistance between the outer casing of the semiconductor diode assembly and the wafer within. Thus, even if the rectifier assembly is immersed in a cooling medium, inefficient cooling results.
Considering these drawbacks, I have developed a rectifier assembly for a synchronous machine which is easily mounted to the housing, insulated from the mounting base, capable of withstanding centrifugal force created at normal operating speeds and is efficiently cooled. The rectifier assembly can be connected to provide either half wave or full wave rectification.